Add the graphics api independent scenegraph port

Opt in via environment variables:
QSG_RHI=1 -> enable using QRhi instead of GL
QSG_RHI_BACKEND -> set to vulkan, metal, d3d11, gl to override the default
(the default is d3d11 on Windows, metal on Mac, gl elsewhere)

Or force a given rhi backend via the existing
QQuickWindow::setSceneGraphBackend().

Otherwise the default behavior is the same as before, the rhi code path
is never active by default.

-no-opengl builds are supported in the sense that they work and default
to the software backend. However, the rhi code path cannot currently be
used in such builds, even though QRhi from qtbase is fully functional
with Vulkan, D3D, or Metal even when qtbase was configured with
-no-opengl. This cannot be utilized by Quick atm due to OpenGL usage
being all over the place in the sources corresponding to the default
backend, and those host the rhi code path as well. This will be cleaned up
hopefully in Qt 6, with the removal all direct OpenGL usage.

Other env.vars.:
QSG_RHI_DEBUG_LAYER=1 -> enable D3D debug or Vulkan validation layer
(assuming the system is set up for this)
QSG_RHI_SHADEREFFECT_DEBUG=1 -> print stuff from ShaderEffect
QSG_SAMPLES=1,2,4,... -> MSAA sample count (but QSurfaceFormat works too)
QT_D3D_ADAPTER_INDEX=0,1,... -> D3D adapter index
QT_VK_PHYSICAL_DEVICE_INDEX=0,1,... -> Vulkan physical device index
QSG_RHI_UINT32_INDEX=1 -> always use uint index data (both
merged/unmerged, convert when needed - with some rhi backends this is
implicit)
QSG_RENDER_LOOP -> to override the render loop as usual. The default
with RHI is threaded for Metal, threaded for Vulkan on Windows, basic
for Vulkan on Linux and Android (to be checked later), while the existing
rules apply for OpenGL.

Not supported when running with QRhi:
  - particles
  - compressed atlases (though this is transparent to the apps)
  - QSGRenderNode
  - QQuickRenderControl
  - QQuickFramebufferObject
  - certain QQuickWindow functionality that depends directly on OpenGL
  - anisotropic filtering for textures
  - native text may lack some gamma correction
  - QSGEngine applicability unclear
  - some QML profiler logs may be incorrect or irrelevant

Change-Id: I7822e99ad79e342e4166275da6e9e66498d76521
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 269 insertions, 0 deletions

diff --git a/src/quick/scenegraph/qsgrhitextureglyphcache.cpp b/src/quick/scenegraph/qsgrhitextureglyphcache.cpp
new file mode 100644
index 0000000000..f181d101c6
--- /dev/null
+++ b/src/quick/scenegraph/qsgrhitextureglyphcache.cpp
@@ -0,0 +1,269 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsgrhitextureglyphcache_p.h"
+#include <qrgb.h>
+#include <private/qdrawhelper_p.h>
+
+QT_BEGIN_NAMESPACE
+
+QSGRhiTextureGlyphCache::QSGRhiTextureGlyphCache(QRhi *rhi, QFontEngine::GlyphFormat format, const QTransform &matrix)
+    : QImageTextureGlyphCache(format, matrix),
+      m_rhi(rhi)
+{
+    // Some OpenGL implementations, for instance macOS, have issues with
+    // GL_ALPHA render targets. Similarly, BGRA may be problematic on GLES 2.0.
+    // So stick with plain image uploads on GL.
+    m_resizeWithTextureCopy = m_rhi->backend() != QRhi::OpenGLES2;
+}
+
+QSGRhiTextureGlyphCache::~QSGRhiTextureGlyphCache()
+{
+    if (m_resourceUpdates)
+        m_resourceUpdates->release();
+
+    delete m_texture;
+
+    // should be empty, but just in case
+    qDeleteAll(m_pendingDispose);
+}
+
+QRhiTexture *QSGRhiTextureGlyphCache::createEmptyTexture(QRhiTexture::Format format)
+{
+    QRhiTexture *t = m_rhi->newTexture(format, m_size, 1, QRhiTexture::UsedAsTransferSource);
+    if (!t->build()) {
+        qWarning("Failed to build new glyph cache texture of size %dx%d", m_size.width(), m_size.height());
+        return nullptr;
+    }
+
+    if (!m_resourceUpdates)
+        m_resourceUpdates = m_rhi->nextResourceUpdateBatch();
+
+    // The new texture must be cleared to 0 always, this cannot be avoided
+    // otherwise artifacts will occur around the glyphs.
+    QByteArray data;
+    if (format == QRhiTexture::RED_OR_ALPHA8)
+        data.fill(0, m_size.width() * m_size.height());
+    else
+        data.fill(0, m_size.width() * m_size.height() * 4);
+    QRhiTextureSubresourceUploadDescription subresDesc(data.constData(), data.size());
+    subresDesc.setSourceSize(m_size);
+    m_resourceUpdates->uploadTexture(t, QRhiTextureUploadEntry(0, 0, subresDesc));
+
+    return t;
+}
+
+void QSGRhiTextureGlyphCache::createTextureData(int width, int height)
+{
+    width = qMax(128, width);
+    height = qMax(32, height);
+
+    if (!m_resizeWithTextureCopy)
+        QImageTextureGlyphCache::createTextureData(width, height);
+
+    m_size = QSize(width, height);
+}
+
+void QSGRhiTextureGlyphCache::resizeTextureData(int width, int height)
+{
+    width = qMax(128, width);
+    height = qMax(32, height);
+
+    if (m_size.width() >= width && m_size.height() >= height)
+        return;
+
+    m_size = QSize(width, height);
+
+    if (m_texture) {
+        QRhiTexture *t = createEmptyTexture(m_texture->format());
+        if (!t)
+            return;
+
+        if (!m_resourceUpdates)
+            m_resourceUpdates = m_rhi->nextResourceUpdateBatch();
+
+        if (m_resizeWithTextureCopy) {
+            m_resourceUpdates->copyTexture(t, m_texture);
+        } else {
+            QImageTextureGlyphCache::resizeTextureData(width, height);
+            QImage img = image();
+            prepareGlyphImage(&img);
+            QRhiTextureSubresourceUploadDescription subresDesc(img);
+            const QSize oldSize = m_texture->pixelSize();
+            subresDesc.setSourceSize(QSize(qMin(oldSize.width(), width), qMin(oldSize.height(), height)));
+            m_resourceUpdates->uploadTexture(t, QRhiTextureUploadEntry(0, 0, subresDesc));
+        }
+
+        m_pendingDispose.insert(m_texture);
+        m_texture = t;
+    }
+}
+
+void QSGRhiTextureGlyphCache::beginFillTexture()
+{
+    Q_ASSERT(m_uploads.isEmpty());
+}
+
+void QSGRhiTextureGlyphCache::prepareGlyphImage(QImage *img)
+{
+    const int maskWidth = img->width();
+    const int maskHeight = img->height();
+    const bool supportsBgra = m_rhi->isTextureFormatSupported(QRhiTexture::BGRA8);
+    m_bgra = false;
+
+    if (img->format() == QImage::Format_Mono) {
+        *img = img->convertToFormat(QImage::Format_Grayscale8);
+    } else if (img->depth() == 32) {
+        if (img->format() == QImage::Format_RGB32 || img->format() == QImage::Format_ARGB32_Premultiplied) {
+            // We need to make the alpha component equal to the average of the RGB values.
+            // This is needed when drawing sub-pixel antialiased text on translucent targets.
+            for (int y = 0; y < maskHeight; ++y) {
+                QRgb *src = (QRgb *) img->scanLine(y);
+                for (int x = 0; x < maskWidth; ++x) {
+                    int r = qRed(src[x]);
+                    int g = qGreen(src[x]);
+                    int b = qBlue(src[x]);
+                    int avg;
+                    if (img->format() == QImage::Format_RGB32)
+                        avg = (r + g + b + 1) / 3; // "+1" for rounding.
+                    else // Format_ARGB_Premultiplied
+                        avg = qAlpha(src[x]);
+
+                    src[x] = qRgba(r, g, b, avg);
+#if Q_BYTE_ORDER != Q_BIG_ENDIAN
+                    if (supportsBgra) {
+                        m_bgra = true;
+                    } else {
+                        // swizzle the bits to accommodate for the RGBA upload.
+                        src[x] = ARGB2RGBA(src[x]);
+                        m_bgra = false;
+                    }
+#endif
+                }
+            }
+        }
+    }
+}
+
+void QSGRhiTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph, QFixed subPixelPosition)
+{
+    QRhiTextureSubresourceUploadDescription subresDesc;
+    QImage mask;
+
+    if (!m_resizeWithTextureCopy) {
+        QImageTextureGlyphCache::fillTexture(c, glyph, subPixelPosition);
+        mask = image();
+        subresDesc.setSourceTopLeft(QPoint(c.x, c.y));
+        subresDesc.setSourceSize(QSize(c.w, c.h));
+    } else {
+        mask = textureMapForGlyph(glyph, subPixelPosition);
+    }
+
+    prepareGlyphImage(&mask);
+
+    subresDesc.setImage(mask);
+    subresDesc.setDestinationTopLeft(QPoint(c.x, c.y));
+    m_uploads.append(QRhiTextureUploadEntry(0, 0, subresDesc));
+}
+
+void QSGRhiTextureGlyphCache::endFillTexture()
+{
+    if (m_uploads.isEmpty())
+        return;
+
+    if (!m_texture) {
+        QRhiTexture::Format texFormat;
+        if (m_format == QFontEngine::Format_A32 || m_format == QFontEngine::Format_ARGB)
+            texFormat = m_bgra ? QRhiTexture::BGRA8 : QRhiTexture::RGBA8;
+        else // should be R8, but there is the OpenGL ES 2.0 nonsense
+            texFormat = QRhiTexture::RED_OR_ALPHA8;
+
+        m_texture = createEmptyTexture(texFormat);
+        if (!m_texture)
+            return;
+    }
+
+    if (!m_resourceUpdates)
+        m_resourceUpdates = m_rhi->nextResourceUpdateBatch();
+
+    m_resourceUpdates->uploadTexture(m_texture, m_uploads);
+    m_uploads.clear();
+}
+
+int QSGRhiTextureGlyphCache::glyphPadding() const
+{
+    return 1;
+}
+
+int QSGRhiTextureGlyphCache::maxTextureWidth() const
+{
+    return m_rhi->resourceLimit(QRhi::TextureSizeMax);
+}
+
+int QSGRhiTextureGlyphCache::maxTextureHeight() const
+{
+    if (!m_resizeWithTextureCopy)
+        return qMin(1024, m_rhi->resourceLimit(QRhi::TextureSizeMax));
+
+    return m_rhi->resourceLimit(QRhi::TextureSizeMax);
+}
+
+void QSGRhiTextureGlyphCache::commitResourceUpdates(QRhiResourceUpdateBatch *mergeInto)
+{
+    if (m_resourceUpdates) {
+        mergeInto->merge(m_resourceUpdates);
+        m_resourceUpdates->release();
+        m_resourceUpdates = nullptr;
+    }
+
+    // now let's assume the resource updates will be committed in this frame
+    for (QRhiTexture *t : m_pendingDispose)
+        t->releaseAndDestroyLater(); // will be releaseAndDestroyed after the frame is submitted -> safe
+
+    m_pendingDispose.clear();
+}
+
+bool QSGRhiTextureGlyphCache::eightBitFormatIsAlphaSwizzled() const
+{
+    // return true when the shaders for 8-bit formats need .a instead of .r
+    // when sampling the texture
+    return !m_rhi->isFeatureSupported(QRhi::RedOrAlpha8IsRed);
+}
+
+QT_END_NAMESPACE